Synthesis of alkylhalosilanes



2,865,939 Patented Dec. 23, 1958 ice 2,865,939 SYNTHESIS OF ALKYLHALOSILANES Ernest L. Little, Jr., and Miller C. Nelson, Wilmington,

el., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Application July 10, E56 Serial No. 596,843

Claims. 01. 260448.2)

This invention relates to a new process for preparing organo-silicon compounds and more particularly to a method of preparing alkylhalosilanes. It is also concerned with novel long-chain alkylhalosilanes.

Alkylhalosilanes have recently acquired considerable industrial importance. These products are very reactive for petroleum in the alkyl chain.

Many methods have ture of alkylhalosilanes comings.

The Grignard synthesis has also been used for preparmg alkylchlorosilanes. This synthesis possesses the disadvantage that it requlr by adding olefins to silicochloroform at elevated tem peratures and pressures. This process is of limited use in bringing about the addition of more than one organic group to the silicon atom.

Another method of of an organic chloride chain alkylhalosilanes.

A further object is provision of a method for synthesizing alkylhalosilanes which avoids the defects of the prior art.

Another object is provision of useful, long-chain alkylhalosilanes which have not been prepared hereto- The above-mentioned and yet further objects are achieved in accordance with this invention by a process which broadly comprises heating together, at a temperature of at least 225 C.,and at ment of group IV of the periodic system having an atomic number of from 14 to 50, inclusive, X is a halogen of conducted in the temperature range of 225 atomic number 17 vessel is heated to the desired temperature.

The principal variables connected with the process are the reactants and their quantities, the perature, and the time of the reaction.

. Many reactants areuseful in this process.

employed has preferably 2-8 carbon atoms and but one cyclic or non-cyclic. Suitable olefins include ethylene, isopropylene, butene-l, butene-Z, isobutylene, the penincluding the Usable halides of the quadrivalent or group IV metals include the inorganic chlorides, bromides, and iodides of silicon, titanium, zirconium, germanium, and tin. Suband may be saturated aliphatic or aromatic. Thesaturated aliphatic. groups may be straighta or branched-chain or cyclic. c The quantities of each reactant used in the process may vary over a wide range.

sufiicientquantity to of the alkylchlorosilanes. The mole ratio of silicide to syntheses. given in one of the examples below.

The time employed in the reaction of the invention may vary between about 4 hours and 48 hours. longer reaction times'within this period favor increased yields and chain lengths but additional time serves purpose.

pressure, the tem- .1 and as high as 1..

little 7 Pressures "above about 150 atmospheres are needed,

higher pressures resulting in increased yield of alkylchlorosilanes. Thus yields, in parts by weight, of high boiling alkylchlorosilanes obtained at 200, 300, and 400 atmospheres under otherwise comparable conditions were, respectively, 23.1, 56.0 and 50.0.

The liquid residues obtained as one of the principal products in the process of'this invention are mixtures of high-boiling, long-chain allgylhalosilanes whose average molecular weight lies between about 450 and about 2200. The silicon contents of the liquid residues are between about 1.3% and'about 5.0% by weight. They react with water to form chlorine-free, viscous liquids soluble in benzene or ether. Since the hydrolyzed products are chlorine-free, the compounds are believed to contain -SiCl groups. i l

The mechanism of the reaction is not clear. The silicon present in the alkali or alkaline earth metal silicide enters into the reaction, as shown by the result obtained when titanium tetrachloride is used. The long alkyl chains attached to the silicon in the liquid residues may result ,from partial polymerization of the olefin prior to reaction with the other components in the process. Alternatively or additionally, initial reaction of some of the olefin with the silicide may occur to yield products which then react further with the olefins to build up the alkyl chain length; Hydrogen required to balance the reaction is obtained from the olefin.

The following examples are submitted to illustrate, but not to limit, various aspects of the invention. In these examples quantities of materials are given in parts by weight, superatmospheric pressure in atmospheres, and subatmospheric pressures in mm. of mercury. Boiling points, unless otherwise noted, were taken at atmospheric ressure.

Example I This example shows a typical preparation of sodium silicide and an embodiment ofth'e invention in which silicon tetrachloride, ethylene and sodium silicide are reacted together. i

(a) A reaction .tube six-inch section of /4" stainless steel pipe with a cap threaded to the bottom. The cap for the top end of the tube is a 34" pipe cap to which one end of a stainless steel tube in diameter and 8" long is welded. The reaction tube is purged with nitrogen gas and charged with 8 grams of sodium met al and 20 grams of silicon powder. The cap with the stainless steel exit tube is then attached and the reaction vessel suspended in a 2" by 12" tube furnace. A rubber tube serves to connect the stainless steel ex t t which is attached to a gas bubbler filled with white 011, the other, to a nitrogen tank. The nitrogen fiow is adjusted until a slow stream of bubbles appears in the white oil. The tube is heated at 700 C. for twenty-four hours, cooled to 600 ,C., maintained at 600 Cifor twenty-four hours, and then cooled to room temperature. The tube is removed from the furnace, the top cap removed and benzene added to the contents.- The product, sodium silicide, is transferred to a receptacle and kept under benzene until used. The product is a gray-black solid which reacts readily with water.

(b) Two hundred and ninety-six (296) parts of silicon tetrachloride and 20.4 parts of sodium silicide were placed'in a stainlessl steelshaker tube (capacity, 400 parts of water). Ethylene gas was pressured into the reaction is prepared which consists of. a

tubeto a glass .T-tube, oneleg had the following composition: C, 79.51%;

225 C. at 500 atmospheres The reaction mass was fil- The liquid filtrate condistilled with the Boiling Yield of Fraction Point, G. Product,

parts A 54-60 114. 0 B 124-133 8. 7 140-170 7. 4 D 0 IIIIIIIII Residue 35.

Fraction A was shown to be unreacted silicon tetrachloride. Fraction B was identified by infrared spectra as a mixture of ethyltrichlorosilane and diethyldichlorosilane, composed of 12.18% carbon, 3.30% hydrogen, 64.53% chlorine, and 16.39% silicon. Fraction C contained alkylchlorosilanes with alkyl chains more than two carbon atoms in length.

The residue, fraction D, which comprised 68.5% of the total product, was a viscous liquid found by analysis to contain 71.48% carbon, 11.98% hydrogen, 11.34% chlorine, and 4.73% silicon, and to have a molecular weight of 625. These data show that the liquid is a mixture of long-chain alkylchlorosilanes whose average composition corresponds to the formula C3qH 15SiCl2. The viscous liquid was readily soluble in ether, benzene, and other organic solvents.

Example II This example shows the reaction between methyltrichlorosilane, ethylene, and sodium silicide.

Two hundred and twenty (220) parts of methyltrichlorosilane, 75 parts of ethylene, and 20 parts of sodium silicide were reacted in a stainless steel bomb at 250 C. and autogenous pressure for sixteen hours. Distillation of the reaction product yielded 34.9 parts of a mixture of alkylchlorosilanes boiling from 105 C. to 185 C. The residue, boiling above 185 C., weighed 27.3 parts and had the following composition: C, 79.45%; H, 13.18%; Cl, 3.33%; Si, 3.24%; molecular weight, 495.

Example 111 This example shows the reaction between dimethyldichlorosilane, ethylene, and sodium silicide.

Dimethyldichlorosilane, ethylene, and sodium silicide were reacted in the same proportions and under the same conditions as in Example II; A mixture "of alkylchlorosilanes was obtained that weighed 5.3 parts and boiled from 145 to 155 C. at 10 mm. pressure. The residue, boiling above 155 C, at 10 mm., weighed 33 parts and H, 13.22%:

Si, 4.04%; Cl, 3.21%; molecular weight, 740.

Example IV This example shows the reaction between trimethylchlorosilane, ethylene, and sodium silicide.

Trimethylchlorosilane, ethylene, and sodium silicide were reacted in the same proportions and under the same conditions as in Example 11. ,The reaction product yielded a mixture oialkyichloro-silanes weighing six parts and boiling from to C. at 10 mm. pressure. A liquid residue, boiling above 115C. at 10 mm. pressure, was also obtained which weighed 32 parts and had the following composition: C, 81.84%; H, 13.74%; St. 2.86%; Cl, 1.84%; molecular weight, 2140.

Example V This example, in effect, shows the increase in chain length with reaction time.

Example -1 discloses that the reaction of ethylene with silicon tetrachloride and sodium silicide yields, in addition to the maior product of high boiling alkylchlorosilanes, a small amount ofalltylchlorosilanes boiling from assesses Example Vl This example shows the reaction between silicon tetrachloride, propylene, and sodium silicide.

Two hundred and twenty (220) parts of silicon tetrachloride, 75 parts of propylene, and parts of sodium silicide were reacted at 300 C. and autogenous pressure for sixteen hours. Distillation of the liquid reaction product yielded 122 parts of unreacted silicon tetrachloride, 10.5 parts of mixed alkylchlorosilanes boiling from 100 to 180 C., and 21.1 parts of a liquid residue boiling above 180 C. Analysis of the residue gave the following results: C, 80.45%; H, 13.39%; Cl, 3.66%; Si, 2.73%.

about 120 to 170 alkylchlorosilanes,

Example VII This example shows the employment of titanium tetrachloride in the process of the invention.

One hundred and seventy (170) parts of titanium tetrachloride and 20 parts of sodium silicide were placed in a 400 ml. stainless steel tube and ethylene gas pressured into the tube for sixteen hours while it was heated at 225 C. and 500 atmospheres pressure. Distillation of the reaction mixture yielded 42.2 parts of alkylthlorosilanes boiling from 150 C. at atmospheric pressure to over 123 C. at 0.8 mm. pressure. A fraction, boiling at 53 to 123 C.'at 0.8 mm., was analyzed and gave the following data: C, 85.31%; H, 13.82%; Si, 1.28%; and Cl, 1.32%.

Example VIII This example shows the substitution of calcium silicide for sodium silicide in the process of the invention.

Two hundred and twenty (220) parts of silicon tetrachloride, 75 parts of ethylene, and 20 parts of calcium silicide were reacted as in Example I at 250 C. and autogenous pressure for sixteen hours. A yield of 24 parts of alkylchlorosilanes, boiling from 120 C. to over 170 C. was obtained with the composition: C, 81.03%; H, 13.56%; Cl, 4.75%; Si, 2.55%. The molecular weight of this product was 610.

Example IX This example shows the use of magnesium silicide rather than sodium silicide in the invention,

The process was run as in Example VIII, using magnesium silicide instead of calcium silicide. A yield of 13 parts of alkylchlorosilancs, boiling from 120 C. to over 170 C., was obtained. The product had the following analysis: C, 82.88%; H, 13.91%; Cl, 3.30%; and Si, 2.27%.

ExampleX This example shows that the long-chain alkylchlorosilanes prepared by the methods given are elfective agents for waterproofing masonry materials.

An ordinary building brick was sawed into eight pieces which were approximately 2-inch cubes, each cube having an unsawed surface which in the parent brick in a building would normally be exposed to the weather. This surface was brushed with a 4% solution of an alkylchlorosilane in toluene, the silane having an average molecular formula of C H SiCl The treated side of the cube was sealed to one end of a hollow glass cylinder 14 inches long by 1.2 inches in diameter and open at both ends, a molten 1:1 beeswax:rosin mixture being used 6 as the cement. A control cube was prepared for test at the same time. After three hours water was-poured to a height of 12 inches in each cylinder in a vertical position resting on the brick base. The drop in water levels after twenty-four hours was used as a measure of waterproofness. The following results were obtained:

Level, Inches None C37H75S1Cl2 The alkylchlorosilanes are also useful in waterproofing paper and as treating agents for canvas and leather.

It will be seen that the process of the invention has several advantages, generally paralleling the objects. Thus by means of it, readily available, lower olefins are transformed into high molecular weight, long-chain alkylhalosilanes. The process is also simple and easily operated and does not produce hazardous by-products. Finally, the process has the distinct advantage of producing long-chain alkylhalosilanes which have not been prepared by any previously-known processes.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The method of producing organohalosilanes which consists of reacting, at a temperature of at least 225 C. and a pressure of at least atmospheres, (1) an olefinic hydrocarbon having a single point of ethylenic unsaturation, (2) the silicide of a member of the group consisting of thealkali and alkaline earth metals, and (3) a compound of the formula MX R where M is an element of the group consisting of silicon, titanium,

halogen of atomic number, 17 to 53, inclusive, R is a hydrocarbon radical having l6 carbon atoms, and n is an integer from 1 to 4, inclusive.

2. The method of claim 1 in which the olefinic hydrocarbon is cyclic.

3. The method of claim 1 in which the temperature is about 225-400 C.

4. The method of claim 1 in which the pressure is about 200-500 atmospheres.

5. The method of claim 1 in which the carbon possesses 2-8 carbon atoms.

6. The method of claim 1 in which the silicide is sodium silicide.

7. The method of calcium silicide.

8. The method of claim 1 magnesium silicide.

9. The method chloride.

10. The method of claim 1 employing titanium tetrachloride.

olefinic hydro claim 1 in which the silicide is in which the silicide is of claim 1 employing silicon tetra- References Cited in the tile of this patent 

1. THE METHOD OF PRODUCING ORGANOHALOSILANES WHICH CONSISTS OF REACTING, AT A TEMPERATURE OF AT LEAST 225*C. AND A PRESSURE OF AT LEAST 150 ATMOSPHERES, (1) AN OLEFINIC HYDROCARBON HAVING A SINGLE POINT OF ETHYLENIC UNSATURATION, (2) THE SILICIDE OF A MEMBER OF THE GROUP CONSISTING OF THE ALKALI AND ALKALINE EARTH METALS, AND (3) A COMPOUND OF THE FORMULA MXNR4-N WHERE M IS AN ELEMENT OF THE GROUP CONSISTING OF SILICON, TITANIUM, ZIRCONIUM GERMANIUM AND TIN X IS A HALOEN OF ATOMIC NUMBER, 17 TO 53, INCLUSIVE, R IS A HYDROCARBON RADICAL HAVING 1-6 CARBON ATOMS, AND N IS AN INTEGER FROM 1 TO 4, INCLUSIVE. 